1. Field of the Invention
The present invention relates to an irrigation/aspiration apparatus used in cataract operation for extracting an opaque crystalline lens.
2. Description of Related Art
There is known an irrigation/aspiration apparatus which supplies an irrigation liquid into an eyeball and aspirates the supplied irrigation liquid with eliminated tissue to be discharged out of the eyeball (e.g., see Japanese Patent Application Unexamined Publication No. Hei 10-43229). The irrigation/aspiration apparatus is used in cataract operation for extracting an opaque crystalline lens. In cataract operation, phacoemulsification which uses a handpiece for fragmentation by means of ultrasonic vibrations (hereinafter, referred to as a US (Ultra Sound) handpiece) is in common use on the ground that phacoemulsification needs only a small incision, and for other reasons.
In phacoemulsification, nucleus of the crystalline lens is fragmented and emulsified by means of ultrasonic vibrations of a US chip attached to the tip of the US handpiece. At the time of fragmentation and emulsification, an irrigation liquid is supplied into the eyeball from the vicinity of the tip of the US chip connected to an irrigation tube. Aspiration pressure is applied to an aspiration tube, one end of which is connected to the Us handpiece by an aspiration pump and the like. The fragmented nucleus of the crystalline lens and the irrigation liquid are aspirated through an aspiration hole of the US handpiece (the US chip) and discharged out of the other end of the aspiration tube.
In phacoemulsification, at the time of aspirating the nucleus of the crystalline lens fragmented by the US chip, if the application of the aspiration pressure by the aspiration pump is continued in a state that the nucleus of the crystalline lens and the like block the aspiration hole of the US chip, the aspiration pressure inside the aspiration pump increases. When the blocking objects such as the nucleus of the crystalline lens on the handpiece are suddenly removed (aspirated) in this state, sharp decrease of pressure of an anterior chamber (surge) temporarily occurs immediately thereafter. When the pressure of the anterior chamber enormously decreases, the anterior chamber is easily deformed. If the anterior chamber is deformed, a corneal endothelium makes contact with the tip of the US chip and the like, and thereby there is a possibility that the corneal endothelium is damaged.
As a measure against the above problem, the above-cited document proposes providing a chamber for storing the irrigation liquid having an air chamber and capable of storing the irrigation liquid, on a channel of the irrigation tube for supplying the irrigation liquid. A technique of the cited document can prevent the sharp decrease of the pressure of the anterior chamber; however, further improvements such as reducing a trouble for an operator, facilitating handling, simplifying a constitution, achieving cost effectiveness and the like are desired.